1. Field of the Invention
The present invention relates, in general, to a mold for fabricating a barrier rib and a method of fabricating a two-layered barrier rib using the same and, more particularly, to a mold for fabricating a barrier rib that includes a plurality of tapered protruding parts and recessed parts having a shape corresponding to embossed portions of the barrier rib, and a method of fabricating a two-layered barrier rib for inkjet application using the same through a low-cost simple process.
2. Description of the Related Art
As shown in FIG. 1, a conventional barrier rib for display devices has a vertically and horizontally striped structure so as to discriminate RGB pixels on a transparent glass substrate 2. A space between the barrier ribs is empty and the adjacent surface is flat and transparent to at least one wavelength so that light penetrates it. In a color filter for liquid crystal displays, an organic black matrix formed on the glass substrate may be exemplified as an application of barrier rib structure.
Methods of fabricating the color filter for liquid crystal displays is classified into various methods, such as a pigment dispersion method, a printing method, a dyeing method, an electrode position method, a photolithographic method, and an inkjet printing method. Among them, the inkjet printing method has drawn much attention from the display industries in recent years because it has advantages in that, since it is possible to simultaneously produce red (R), green (G), and blue (B) color filters, the process is simple, the amount of material used is reduced, and thus the production cost is low.
According to the inkjet printing method, predetermined patterns, what is commonly called a barrier rib structure formed on a substrate, are prepared and the recessed parts of the barrier rib are filled with colored resins (R, G, and B) to fabricate a color filter. When an embossing process or an imprinting process employed for fabricating barrier ribs, a deformable composition for the barrier rib is pressed using the mold having a predetermined pattern, and cured, and the mold is removed, thereby forming the barrier rib structure on the substrate. In other words, it is possible to apply the embossing process to fabricate a micropattern or a barrier rib. The embossing process may be classified into a thermal embossing process, in which curing is conducted by temperature variation, and a UV embossing process, in which curing is conducted by UV radiation, according to a method of forming a solidified pattern. In the thermal embossing process, if material of the barrier rib is thermoplastic, the material is heated at a glass transition temperature or higher so as to be deformable or fluidic at the molding temperature, pressure is applied thereto to conduct embossing, the resulting material is solidified (more strictly speaking, glassified) by cooling after a pattern is formed, and the mold is removed. Meanwhile, when using thermosetting material, the material of the barrier rib having fluidity is embossed, heated, and cured, and then the mold is removed.
With respect to a conventional method of preventing the nonuniform spread or mix-up between the adjacent pixels and staining of the barrier rib's surface by resins of color filter printed in an inkjet manner, Japanese Patent Laid-Open Publication No. 2001-42313 discloses a method of neatly applying ink to an ink receiving structure between barrier ribs (see FIG. 2).
In other words, as shown in FIG. 2, a barrier rib is patterned on a glass substrate 11 using photolithographic methods so as to have a structure consisting of two layers 12, 13. A lower layer 12 of the barrier rib is made of a hydrophilic material that has affinity to hydrophilic ink and an upper layer 13 is made of hydrophobic material that has an aversion for ink so that the glass substrate 11 easily receives ink, and vice versa in the case of water-based ink. However, if the barrier rib is fabricated through the above methods, undesirably, a plurality of complicated coatings, mask aligning steps and exposure processes must be carried out.
Furthermore, there exist methods of employing materials having different surface properties or of conducting treatment using them so as to easily receive ink through a procedure similar to that of Japanese Patent Laid-Open Publication No. 2001-42313 as described above. For example, Japanese Patent Laid-Open Publication No. 2000-89022 discloses a method of conducting exposure while an ink receiving layer is hidden using a black matrix made of a resin composition having a light blocking property. Japanese Patent Laid-Open Publication No. 2000-28819 discloses a method of polishing an ink receiving layer to flatten it, Japanese Patent Laid-Open Publication No. Hei. 11-194211 discloses a method of forming a second layer on a metal black matrix. Korean Patent Laid-Open Publication No. 2001-110183 discloses a surface treatment method using a plasma.
However, all of the above methods need at least one additional photolithography process which incurs a high cost, particularly because of a surface treatment or the use of costly devices and fine chemicals in great quantities. Therefore, there remains a need to develop a mold capable of fabricating a barrier rib employing a simple low-cost process and an embossing method of fabricating the barrier rib using the mold.